Annealing furnace and method of annealing



April 19, 1938. HUFF I 2,114,382

ANNEALING FURNACE. AND METHOD OF ANNEALING Filed Oct. 22, 1957 2 Sheets-Sheet 1 ii-i T 4 E .Er l IL. 1 +4 I:

a :1 INVENTOR.

' BY 5, 44? M/z/M ATTORNEYS.

April 19, 1938.

F I l l l I l I Filed Oct. 22, 1937 'L fl 2 Sheets-Sheet 2 INVENTOR. MMW

ATTORNEYS.

Patented Apr. 19 1938 UNITED sTATEs 2,114,382 ANNEALING F%QA 1g) METHOD or Edward I. ma, Pittsburgh, Pa.

Application October 22, 1937, Serial No. 170,332

3 Claims.

My invention relates to the annealing of metal,

and consists in an. annealing furnace and amethod of operation, particularly adapted to the annealing of flat sheets of steel. Theobjects are 5 economy in furnace construction and in operation, and excellenceof product.

The invention is illustrated in the accompanying drawings. Fig. I is a view of a furnace of the invention, partly in plan from above and partly in horizontal section; and Fig. II is a view of the furnace in vertical section and to larger scale,

the plane of section being indicated at II-1I in F18. I. j

Referring to the drawings, the furnace is of mufile type and includes an outer heat-insulating wall I and roof l0, and an inner heat-conducting muille 2. The muffle is 'a thin-walled shell of metal. It is spaced from, the side walls and roof of the furnace, and in such space the heat-affordingflames may be developed. Within the muflie 2 the material to be treated is enclosed.

In modern practice ingots and billets ,of. steel are reduced in continuous operation to highly attenuated sheets. On the completion of the rolling operation, the sheets, trimmed to particular size or not, are arranged in stacks and subjected to tlie requisite annealing operation.

The operation of annealing consists in heating the material to a peak temperature and cooling it again; and, while rate of heating, peak temperature, time at peak, and rate of cooling must,

in order to attain desired results, conform to a certain standard, there is a margin of tolerance; and if throughout all its extent each sheet in its treatment be brought within such margin, the product will be of uniform quality. In the operation of the furnace of my invention the'material is so brought within themargin of tolerance, and the annealed product is of uniform and standard The muille 2 is of usual structure in that it consists ofintegral and imperforate side and top walls, is open at bottom, and is adaptedto rest upon a horizontal base; enclosing the material to 13 be treated-a stack of sheets 8 in this case. The proportion'ing of the muiiie to the stack is a matter that admits of variation, and itwill be understood that insuch particulars the showing is exemplary merely.

0 The muille in the assembly rests upon a pan 3,

and the pan 3 horizontally upon the hearth 4 of the furnace. The pan is doubly flanged at its margin (cf. double flange 30), and the lower edge of the muille engages the bottom of the pan between these flanges, and luting Lis applied, as

hearth 4 into the combustion shown in Fig. II. A rectangular block 5, arranged within the margins of pan 3, may ail'ord support for a rectangular stool '6, upon which the charge sists in a box-like hood, constructed essentially of heat-insulating brick, externally braced and reinforced by means of structural steel. Other-' wise closed, it is operi at botton and is applicable to and removable from the stationary and horizontally extending hearth 4. The walls of insu-v lating material are built within a supporting shell I I of sheet metal, and this shell of metal, extending downward, enters a channel llll formed-in the hearth, wherein luting IL is provided (Fig. II). As shown, the box-like hood is provided with a perforate lug 22, f or the attachment to it of ralsing and lowerlngmechanism.

When the movable parts of the furnace are as-- sembled over the packof sheets S seated on the hearth-stool 6, there is, as has been said, a space between the walls of the muflie 2 and-the walls I, ,III of the hood. In accordance with the invention, the spaces or regions C, C between the opposite side walls of the mufile and the side walls of I the hood are employed as the primary, if not the Burnsole, combustion chambers for the fuel. ers l are arranged in each of the opposite end walls of the elongate and relatively narrow hood; in service these burners direct burning columns of fuel and air into the regions C, C; in each of the elongate and relatively narrow regions C, C on opposite sides of the muflle 2 the burning columns are directed inward, toward the vertical mid- -plane of the furnace, and the walls of mufile are heated. Observation ports 8 may be provided in the walls, above the burners.

Each of theopposite side walls i of the hood includes a series of flues 9 that, extending vertically, open at their upper ends into horizontal stack-flues 90, embodied in the upper refractory body or roof of the hood. And each flue 90 opens into the atmosphere by way of an outlet 99 which may comprise a short stack, or be connected to a relatively tall stack. The hearth 4 includes a series of transverse flues l2 that establish communication between the combustion zones C, C

and the side-wall flues 9. Each hearth flue l2 opens at one end upward through thev floor of the zone or region C1? muflle to a flue 9 in the left hand wall'of the hood. Thus, a system of hearth flues, arranged in spaced-apart relation longitudinally of the furnace, interconnects the combustion zones 0 with the flues in the opposite side walls of the hood.

It will be perceived that the burners I are located below the horizontal mid-plane of the furnace, with the consequence and effect that the flames, springing from the opposite ends of the regions C, sweep horizontally, adjacent to the hearth of the furnace, toward the centers of such regions C. In the operation of the furnace, the horizontally flowing columns of burning fuel and hot gases are drawn downward into the mouths of hearth flues l2, that are spaced longitudinally of the course of flow. Straying streams of hot gases, meandering upward over the side walls of the muflle and spreading laterally over its end walls, meet and mingle over the top wall of the mufile and beneath the closed roof ll! of the hood, hnd these idly meandering streams distribute heat, by conduction and convection, to the upper side, end and top walls of the muflle. The main bodies of the burning fuel and hot products of combustion are drawn immediately from the regions C, C into the flues I2, and are led transversely through the hearth and introduced to the flues 9 in the side walls of the hood, whence the hot gases rise into the horizontal flues 99 and exit by way of stacks 99.

The heat thus generated in the furnace is concentrated, immediately above and within the hearth upon which the charge S is seated, and the heat given up to the side walls I of the hood so far augments the insulating and refractory capacity of these walls that conduction and convection of heat over and through the upper walls of the mufile, and conduction of heat immediately from the hearth to the base of the charge, become effective to elevate and hold all portions of the charge at desired temperature. The requisite heating of the charge is obtained rapidly and with uniformity throughout the entire charge. In such operation of the furnace the method of my invention is practiced, and by virtue 'of the structure described I achieve advantages in a hood-type furnace that hitherto were only realized, if realized at all, in a stationary furnace of large and costly construction.

An important detail of construction remains for consideration. It will be perceived that the base of the hood fits over and peripherally'encompasses the upper body portion of the hearth 4. Each flue l2, opening upward at one end through the floor of the hearth, as already mentioned, terminates at its opposite end in the side stu'face of the hearth which 'is embraced by the basal wall portion of the hood. There is a clearance 29 (Fig-II) between the body ofthe hearth and such basal wall of the hood, and into this clearance the lower ends of the wall flues 9 of the hood open and communicate with the hearth flues l2. Thus,

organization of hearth and side wall flues is permissible in a furnace of the removable hood type.

I claim as my invention:

1. The herein described method of operating a hood-type annealing furnace including a stack of metal sheets seated upon the furnace hearth and enclosed within a mufiie, which method ineludes introducing burning columns of fuel into the regions between muflle and the opposite side walls of furnace hood, drawing the burning fuel and products of combustion on opposite sides of.

the mufiie downward from the course of fuel delivery, and, while some of the burning fuel and hot products meander upward on opposite sides of the muflie and meet and mingle over the top of the muflie and under the roof of the furnace hood, leading the downwardly drawn products transversely through the hearth upon which said stack of sheets is seated, and then removing such products upward through the side wall of the hood which lies on opposite side of the muflle from that from which said products enter said hearth.

2. An annealing furnace including a hearth for supporting the material to be annealed, a muflle enclosing the material on the hearth, and a hood applicable to and removable from said hearth, said hood having refractory side walls spaced from the walls of said mufile, means for introducing burning columns of fuel into the regions between the side walls of said hood and said muflle, flues in the opposite side walls of said hood, flues extending transversely through said hearth, certain of said hearth flues communicating with the region of combustion on the righthand side of said muflle and extending to and opening into the flues in the left-hand side wall of said hood, and other of said hearth flues establishing communication between the combustion region on the left-hand side of said muflle and the flues in the right-hand side wall of said hood.

3. An annealing furnace including a hearth for supporting the material to be annealed, a muffle.

enclosing the material on the hearth, and a hood applicable to and removable from said hearth, said hood having refractory side walls spaced from the walls of said muil'ie, means for introducing burning columns of fuel into the regions between the side walls of said [hood and said muille, flues in the opposite side walls of said hood, flues extending transversely through said hearth,cer-

tain of said hearth flues communicating with the region of combustion on the right-hand side of said mufile and extending to and opening into the flues in the left-hand side wall of said hood, and other of said hearth flues establishing communication between the combustion region on the left-hand side of said muflle and'the flues in the right-hand side wall of said hood, and stackfluesembodied in the upper structure or roof of said hood, into which stack-flues said flues in the side walls of said hood open.

EDWARD I. HUFF. 

